An electron antineutrino mass has been measured in tritium β-decay in the Troitsk ν-mass experiment. The setup consists of a windowless gaseous tritium source and an electrostatic electron spectrometer. The whole data set acquired from 1994 to 2004 was reanalyzed. A thorough selection of data with the reliable experimental conditions has been performed. We checked every known systematic effect and obtained the following experimental estimate for neutrino mass squared m 2 ν = −0.67 ± 2.53 eV 2 . This gives an experimental upper sensitivity limit of mν < 2.2 eV , 95% C . L. and upper limit estimates mν < 2.12 eV , 95% C .L. for Bayesian statistics and mν < 2.05 eV , 95% C .L. for the Feldman and Cousins approach.

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Measurements of the energy loss of fast electrons at an energy of 18 keV have been performed on molecules of hydrogen isotopes, gaseous T2 and frozen D2. Whereas in the case of gaseous T2 the values of total inelastic cross-section (σtot, gaseous = (3.40 ± 0.07) × 10 −18 cm 2 for E = 18.6 keV), average energy loss (εgaseous = (29.9 ± 1.0) eV) and peak position of the energy loss spectra (ε1, gaseous = 12.6 eV) agree well with the expectations, the corresponding values for quench condensed D2 differ significantly from the ones for gaseous T2. We observe a significant lower total inelastic cross-section (σ tot, solid = (2.98 ± 0.16) × 10 −18 cm 2 , for E = 18.6 keV) larger average energy loss (ε solid = (34.4 ± 3.0) eV) and higher peak position (ε 1, solid = (14.1 +0.7 −0.6 ) eV). These differences may be interpreted in terms of changes of the final state spectrum. A CI calculation for a D2 cluster shows indeed a clear shift of the excited states in agreement with the observation. PACS.34.80.Gs Molecular excitation and ionization by electron impact -78.90.+t Other topics in optical properties, condensed matter spectroscopy and other interactions of particles and radiation with condensed matter

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